1. Field
The present disclosure relates to an apparatus and a method for recovery of target gas, and more particularly, to an apparatus and a method for recovery of target gas, which may increase a target gas concentration in a recovered gas based on a single gas separation membrane module and a plurality of gas storage tanks.
[Description about National Research and Development Support]
This study was supported by Ministry of Trade, Industry and Energy of Korea (Project No. 1415131763; Project name: Development of Separation and Enrichment System for low-concentration SF6 Gas for Semiconductor and Display) under the superintendence of the Korea Institute of Energy Technology Evaluation and Planning.
2. Description of the Related Art
SF6 is a representative electric insulation material of power equipment and is used in a washing process when manufacturing a semiconductor wafer, an LCD panel or the like. It is known that an influence of SF6 on global warming is about 23,900 times higher than that of carbon dioxide, and in the Climatic Change Convention held at Kyoto in 1997, SF6 was pointed out as one of six materials with greatest global warming potentials. Therefore, it is urgently needed to treat SF6.
In order to treat SF6, first, SF6 may be decomposed. Since SF6 is very stable, high energy like plasma is required to decompose SF6, and during the decomposing process, byproducts such as S2F10, SF4, HF or the like with high toxicity and corrosiveness are generated. Considering the above problems in decomposing and increasing prices of SF6, it is very desirable to effectively recover and reuse SF6 in view of reduction of production costs.
In the SF6 recovering technique, only SF6 is recovered from a mixture gas containing SF6. Such SF6 recovering technique includes cyrogenics, PSA (pressure swing adsorption), membrane separation and so on, among which membrane separation method using a gas separation membrane module is being widely studied. The membrane separation method has advantages since it has relatively simple equipment and relatively excellent recovery rate. An example of the membrane separation method is disclosed in Korean Patent Registration No. 10-1249261.
In the membrane separation method, waste gas is injected into a separation membrane module, and the separation membrane module separates the injected waste gas into SF6 (recovered gas) and other gas (permeated gas). The treatment characteristic of the membrane separation method is determined by selectivity and permeability of the separation membrane module. If the separation membrane module has high permeability, a treatment capacity is great. However if the separation membrane has high permeability, selectivity is low and thus separation performance for the recovered gas is low.
As described above, selectivity and permeability of the separation membrane module have a trade-off relation, and thus in the existing technique, a plurality of separation membrane modules is provided in multi stage manners to ensure separation performance and treatment capacity to some extent. However, if a plurality of separation membrane modules is repeatedly provided in multi stages, the configuration becomes complicated. To solve this problem, the applicant of this application has proposed an apparatus which includes two separation membrane modules (a first separation membrane module and a second separation membrane module) so that recovered gas and permeated gas of the first separation membrane module are respectively circulated to increase a recovery rate, in a Korean Patent Application No. 2013-118138.